The primary focus of work in the Molecular Genetics Section continues to be on control of cell proliferation in mammalian cells, with investigation of negative growth regulatory pathways emphasized within this framework. Several results of interest have been obtained. i) The short sequence motif GAGGCNGAGGC, which is partially responsible for growth regulatory properties of 7SL RNA and Alu elements, has been shown to bind a previously undiscovered protein containing tandem C2H2 class zinc fingers of the TFIIIA/Kruppel type. Characterized members of this family are transcription factors and master control genes in early embryogenesis. ii) A serious technical obstacle to use of RNA mobility shift assays in crude nuclear extracts has been overcome: high non-specific binding activity (which in the past completely masked specific RNA-protein interactions) was eliminated by high levels of the homopolymer poly(rG). This finding opens the way for the investigation of small RNA polymerase III-transcribed RNAs as nuclear regulatory factors. iii) Recombinant circle polymerase chain reaction (RCPCR), a novel method for site-specific mutagenesis and other molecular cloning procedures, was developed.